- Mechanism and reactivity in perborate oxidation of anilines in acetic acid
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Perborate but not percarbonate in acetic acid generates peracetic acid on standing and the peracetic acid oxidation of anilines is fast. The oxidation with a fresh solution of perborate in acetic acid is smooth and second order but the specific oxidation rate increases with increasing [perborate]0 or [boric acid]. Perborate on dissolution affords hydrogen peroxide and a borate; the latter assists the former in the oxidation. The oxidation rates of anilines under identical conditions do not conform to any of the linear free energy relationships but the reaction rates of molecular anilines do. Perborate oxidation proceeds via two reaction paths but the overall oxidation rates of molecular anilines conform to structure reactivity relationships; the transition states do not differ significantly. Analysis of the oxidation rates of perborate and percarbonate reveals that while perborate oxidation is faster than percarbonate it is at least as selective as the latter.
- Karunakaran, Chockalingam,Kamalam, Ramasamy
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p. 2011 - 2018
(2007/10/03)
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- Hetero-Cope Rearrangements, III. - Vinylindoles via Hetero-Cope Rearrangement
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The reaction of N-phenylnitrones 1 with allenes 2 which are substituted with electron acceptor groups gives various products via addition and sigmatropic rearrangement depending on the specific acceptor group.In this manner one obtains 2-substituted indoles 8a, 8b, and 10 from propadienyl trichloromethyl sulfoxide.Using phenyl propadienyl sulfone a derivative 4a of tetrahydro-1-benzazepin-4-one is obtained.Reactions with allenecarbonitril proceed via several steps and yield 2-vinylindoles of type 6.Intermediate products could not be isolated.
- Blechert, Siegfried
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p. 673 - 682
(2007/10/02)
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- Investigations on the Kinetics and Mechanism of Polarigraphic Reduction of o-, m- and p-Nitrotoluenes and o-, m- and p-Nitrophenols in the presence of Ionic and non-Ionic Surfactants
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Polarographic behaviour of o-, m- and p-nitrotoluenes (4percent, V/V, ethanolic solution) in the presence of ionic and non-ionic surfactants at their concentrations just sufficient to suppress the maxima has been studied as a function of pH of Britton-Robinson (BR) buffer.The present study aims at investigating the kinetics and mechanism of the reduction of these compounds at the d.m.e. which has been found to be diffusion-controlled and irreversible.The potential-dependent rate constant, kf,h has been calculated by Koutecky's method at different pH values of BR buffer and the values of kinetic parameters (αna and kf,h0) have been calculated from log kf,h Vs Ed.e. plots which are linear thereby suggesting that only a single rate-determining step is involved in the reduction of each depolarizer.Based on the values of kinetic parameter, αna and the variation of E1/2 with pH, the stoichiometry of the rate-determinig step, in each case, has been established thereby leading to the postulation of a mechanism for the polarographic reduction of each depolarizer.
- Singh, M.,Chandra, K.
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p. 977 - 989
(2007/10/02)
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- ELECTROCHEMICAL REDUCTION OF m-NITROPHENOL IN BUFFERED AQUEOUS SOLUTIONS
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A study on the electrochemical reduction of m-nitrophenol on a mercury electrode in buffered aqueous solutions, has been carried out, focusing on the zone of potentials corresponding to the rising portion of the wave (i/iL0.05), whose corresponding kinetic parameters allow us to suggest a reduction mechanism for each of the pH-ranges of 0-1, 1-8.4, 8.4-10.6, and 10.6-13.5.
- Heras, A. M.,Avila, J. L.,Capdevila, F.,Garcia Blanco, F.
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p. 337 - 346
(2007/10/02)
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- Kinetics and Mechanism of Polarographic Reduction of Aromatic Nitro Compounds in Aqueous Alcoholic Medium
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Polarographic reduction of nitrobenzene, ortho-, meta- and para- chloronitrobenzenes, nitrotoluenes, nitrophenols and nitrobenzaldehydes has been studied in 25percent (v/v) aqueous ethanolic solutions, using Britton-Robinson (BR) buffer of varying pH values.KCl (0.1 M) has been used as the supporting electrolyte and Triton X-100 (0.001percent) as the maxima suppressor.The potential-dependent rate constant, kf,h has been calculated by Koutecky's method at different pH values and the values of kinetic parameters (αna and kf,h) have been calculated from logkf,h versus Ed.e. plots which are linear thereby suggesting that only a single rate-determining step is involved in the electrode process of each depolarizer.Based on the values of kinetic parameter, αna and the variation of E1/2 with pH, the stoichiometry of the rate-determining step has been established.This has led to the postulation of a tentative mechanism for the polarographic reduction of each depolarizer.Besides, the effect of the nature and position of various substituents, viz.Cl, CH3, OH and CHO on the kinetics of the polarographic reduction of NO2 group has been investigated.
- Ratan, Ram,Rani, Rama,Singh, Mukhtar
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p. 664 - 670
(2007/10/02)
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- Kinetics of Irreversible Electrode Reactions of o-, m- and p-Nitrophenols at Dropping Mercury Electrode in Presence of Ionic and Non-ionic Surfactants
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Polarographic reduction of o-, m- and p-nitrophenols in 4percent ethanolic solution has been studied at 25+/-0.1 deg C in Britton-Robinson buffer of pH 6.09 in the presence of increasing amounts of some ionic and non-ionic surfactants.The reduction of all
- Chandra, Kailash,Singh, Mukhtar
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p. 579 - 583
(2007/10/02)
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